What are the main concepts of electricity and magnetism?
What are the equations?

Start here:

HyperPhysics

Click on the Electricity and Magnetism balloon.

What are the main equations and when do you know how to use them?

Well, I guess for your level, you have where V is the potential difference, I is the current, R is the net resistance and P is the power dissipated:





And deriving other equations from those two, we get:

and

For the definition of an ampere, the rate of flow of charge;



To define the magnetic force, the force acting on a charge q moving at velocity v at perpendicular direction with the magnetic field B;



The force on a current carrying wire carrying a current I and of length L, perpendicular to a magnetic field B;



Are you looking for more specific formulae?

Could someone explain the equation:

W=Pt=VIt=I[squared]Rt=V[squared]t/R.
Each part is equal to the other, I was just wondering if someone could more thoroughly explain this to me.

Thank's much!

[For electricity.]

You know the definition of power? It's the rate of doing work, or



Rearranging making Work the subject we get;



Now, in electricity, the power dissipated is given by: P = IV.

Replace in the equation for work:



Now, using Ohm's equation, V = IR, you first replace V by IR, giving:



or you replace the I by V/R, since I = V/R, to give:



In other terms, if you have an appliance running at a certain voltage, or at certain current, and you know its resistance and the time it was working, you can find the electrical energy that it used, with that equation.